Rates for urinary bladder tumors are known to be relatively high for Copenhagen, and have proved to considerable extent associated with tobacco smoking. While rates for lung cancer are about half the English, rates for bladder tumors are almost equal in the two countries, although occupational bladder tumors are not known in Denmark, in contradistinction to England. For these reasons a case control study for urinary tract tumors has been established in Copenhagen collaborating with nearly all urological surgical departments in the city. Patients are, as usual, reported to the Cancer Registry which per Oct. 1st, 1979 has provided for interviews with 70 bladder patients and 55 population controls, and with 24 ureter and pelvis cancers with 40 hospital controls. The study is in progress.